Field of the Invention
The present invention relates to a solid-state image sensor and a camera.
Description of the Related Art
A solid-state image sensor including a plurality of two-dimensionally arrayed photoelectric converters is mounted in a digital camera, a digital camcorder, or the like. In the solid-state image sensor, a transfer transistor transfers charges accumulated in the photoelectric converters to a floating diffusion (to be referred to as an FD hereinafter). The FD functions as a charge-voltage converter which converts a charge quantity into a voltage. The gate of an amplifier transistor is connected to the FD. The amplifier transistor outputs, to a column signal line, a signal corresponding to the charge quantity (the potential of the FD) transferred to the FD. The charge quantity that can be transferred to the FD depends on the potential of the FD. Japanese Patent Laid-Open No. 2012-010106 describes that when the FD is in a floating state, the potential of the FD is increased by increasing the potential of the gate of a reset transistor within a range where the reset transistor is not turned on. Increasing the potential of the FD makes it possible to increase the charge quantity that can be transferred to the FD and widen a dynamic range. Note that if the potential of the gate of the reset transistor is increased until the reset transistor is turned on, the reset transistor drives the FD at a predetermined potential. In this state, therefore, it is impossible to read out signals corresponding to the charges of the photoelectric converters even if the charges are transferred to the FD.
As described above, the solid-state image sensor described in Japanese Patent Laid-Open No. 2012-010106 can increase the potential of the gate of the reset transistor only within the range where the reset transistor is not turned on. Therefore, the charge quantity that can be transferred to the FD serving as the charge-voltage converter is limited to be in the range where the reset transistor is not turned on.